Question

If the refractive indices of a prism for red and violet colours are $1.74$ and $1.78$ respectively, then the dispersive power of prism is:

• A. $\frac{1}{24}$
• B. $\frac{1}{19}$
• C. $0.04$
• D. $19$

Answer 1

The correct option is A $\frac{1}{24}$

Dispersive power is given by

$\omega =\frac{n_v-n_r}{n-1}wheren=\frac{n_v+n_r}{2}$

$n=\frac{1.78+1.74}{2}=1.76$

$\omega =\frac{1.78-1.74}{1.76}=\frac{0.04}{1.76}=0.0227$